Yankees' Headley gets first start at first base

SEATTLE -- Chase Headley was busy well before Yankees' batting practice at Safeco Field on Thursday, taking grounders and turning double plays at first base, his new position.

That will likely be Headley's pregame routine for some time, as the longtime third baseman transitions to playing first base to allow newly acquired slugger Todd Frazier regular time at the other infield corner.

SEATTLE -- Chase Headley was busy well before Yankees' batting practice at Safeco Field on Thursday, taking grounders and turning double plays at first base, his new position.

That will likely be Headley's pregame routine for some time, as the longtime third baseman transitions to playing first base to allow newly acquired slugger Todd Frazier regular time at the other infield corner.

"I went in after we had found out about it [trade] right after the game and I told [Yankees manager] Joe [Girardi], 'Hey, whatever the team thinks is best, I'm good with,'" Headley said. "The next day he called me in and said this what we're going to do. That was that. There was really no need to get an explanation. They have their reasons. I said whatever's best for this team was what I was going to do. They thought that was the best thing, and that's where we are at."

Headley had seven putouts, but had trouble corraling a pickoff throw from Luis Severino in the second inning of the Yankees' 4-1 win. Severino was charged with an error on the play.

Headley's move to first base sets up a natural platoon with rookie right-hander Garrett Cooper. The switch-hitting Headley will likely get the nod against right-handed pitchers, as he's struggled from the right side against lefties this season, hitting a .208/.233/.302, while putting up better numbers from the left side against righties -- .279/.382/.399.

Cooper is in line for more at-bats against lefties. He's hitting .250/.250/.417 in 12 at-bats against lefties compared to .111/.111/.223 in nine at-bats against righties.

Even though he knows a platoon is imminent, Headley's preparing each game like he's in the lineup.

"I'm not naïve enough to think that didn't come into play a little bit. Considering I haven't swung the bat very well from the right side this year," Headley said. "My mindset's going to be, 'I'm playing every day.' If I find out I'm not playing, then I'm not playing -- against a lefty or someone like that. But I just think that's the way to prepare and go about it. They're going to make the decisions to put this team in the best position to win, and that's really how it should be."

Most of all, Headley needs to adjust to playing first base, where he's appeared in 12 games since breaking into the big leagues in 2007 with the Padres. Four of those games have come this season.

Girardi has confidence in Headly's transition.

"There's going to be an adjustment period, and there might be some times where he finds himself in the wrong spot, but I think he has a pretty good idea of what he needs to do with his work defensively," Girardi said. "It's just a different feel, and that's the biggest thing. One thing that's going to help him is the experience."

O'Neill's number won't be touched, after all

After saying he'll reach out to former Yankees' outfielder Paul O'Neill about wearing his number No. 21, Frazier said on Thursday that he'll stick with No. 29, which the Yankees gave him. He wore No. 21 while playing in Cincinnati and with the White Sox, but said he's not attached to it.

"It's a great number, but at the end of the day it won't affect me or bother me that much," Frazier said. "I'd like to have that number, but at the end of the day No. 29 is pretty great, too."

Josh Horton is a reporter for MLB.com based in Seattle. He covered the Yankees on Thursday.